When a semiconductor device is manufactured, a semiconductor wafer is generally, repeatedly subjected to various thermal processes such as a film-deposition process, pattern-etching process, oxidation and diffusion process, modification process, annealing process, and so on, so as to manufacture a desired device. In the light of the recent demand for higher density, the increased number of layers, and higher integration of the semiconductor device, the semiconductor device should have strict specifications. In particular, an improvement in a wafer intra-surface uniformity and an improvement in a film quality are desired in the various thermal processes. For example, in a process of a channel layer of a transistor as a semiconductor device, the channel layer is generally subjected to an annealing process with a view to stabilizing an atomic structure, after ion implantation of impurity atoms.
Although the annealing process of the channel layer for a long period of time can stabilize the atomic structure, the long annealing process undesirably causes the impurity atoms to diffuse downward in a film-thickness direction of the channel layer to penetrate the same. Thus, the annealing process should be carried out as briefly as possible. That is, in order to stabilize the atomic structure without penetration of the atoms through the channel layer, while reducing the film-thickness thereof, the semiconductor wafer should be rapidly heated to a high temperature to perform the annealing process, and should be rapidly cooled to a low temperature to prevent diffusion of atoms after completion of the annealing process.
In order that such an annealing process is realized, a conventional thermal processing apparatus is provided, in a lamp house equipped with a heating lamp, with a shutting mechanism for shutting a radiation heat. When a wafer temperature is lowered after the annealing process of a high temperature, the shutting mechanism is so operated as to shut the radiation heat radiated from the heating lamp. Thus, the wafer can be rapidly cooled to a lower temperature.
Another conventional thermal processing apparatus is disclosed in JP2001-85408A in which a Peltier element is disposed on a wafer stage. When a wafer is subjected to an etching process at a temperature of about 100° C. to about 250° C., the Peltier element is utilized to raise or lower the temperature of the wafer.
However, the conventional thermal processing apparatus having the shutting mechanism is disadvantageous in that a bulk of the shutting mechanism enlarges the size of the thermal processing apparatus, and a provision of such bulky shutting mechanism complicates a structure of the thermal processing apparatus. On the other hand, the conventional thermal processing apparatus having the Peltier element is suitable for the etching process using a process temperature as low as 100° C. to 250° C., but the apparatus is insufficient to perform the annealing process of a higher temperature.